If music, speeches, and the like are played in an environment where reverberation can easily occur, such as halls, and are recorded, the recorded acoustic signals often contain not only a direct sound but also a reverberant sound, which is convoluted in during the recording. Therefore, if the acoustic signals into which the reverberant sound has been convoluted are played in another acoustic environment, there is a reduction in the clarity of the direct sound, possibly making it very difficult to listen when the acoustic signals are played.
If a speech sound into which a reverberant sound has been convoluted is used for voice recognition or the like, the problem is that the recognition rate of the speech sound (content) would decrease due to a reduction in the clarity caused by the reverberant sound.
As for the acoustic signals into which the reverberant sound has been convoluted as described above, a conventional technique has been known to reduce the reverberant sound (See Patent Literature 1, for example). The use of the technique makes it possible to clarify the direct sound by reducing the reverberant sound.